Mechanisms of sorption in the near field

A number of synthetic compounds have been prepared which represent those which are considered to be present in a mature BFS/OPC cement. Some of these have been prepared with lanthanum dopant to investigate the possible inclusion of sorbed species in the structure. The compounds have been investigated by the best available tools to determine the chemical state of the sorbed species and the possible incorporation of the sorbed ions into the evolving structure of the cement. The sorption coefficients of these compounds for americium and plutonium have also been determined. The structural studies were impeded by the instability of the compounds and the surface analytical tools lacked the sensitivity to detect the sorbed elements. The extended X-ray absorption fine structure (EXAFS) technique shows considerable promise. Studies of the sorption of actinides from solution onto these compounds have shown that the sorption coefficients are no less than those determined for fresh cements. (author)